Vitamin D will not help prevent colds

Taking Vitamin D supplements will not help prevent the common cold, University of Otago researchers say.

Some studies have suggested vitamin D - most commonly obtained from sunshine - can boost the immune system and help prevent colds, some cancers and heart disease.

However, researchers at the University of Otago in Christchurch say there is still a lack of clear scientific evidence to support many of the claims.

A new paper on the effect of vitamin D on the common cold, published today in the Journal of the American Medical Association, found taking vitamin D supplements did not result in participants having fewer or less severe episodes of upper respiratory tract infections.

The research involved 322 healthy adult Cantabrians taking either a placebo pill or a vitamin D pill every month for a year and a half.

The researchers measured the number and severity of participants' colds during that time and found no statistical difference between those taking placebo pills and those given vitamin D supplements.

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Principal investigator Professor David Murdoch said there had been ''a lot of type'' regarding the potential of vitamin D to prevent infections, including the common cold, but this was the first study to convincingly show the vitamin did not prevent colds in healthy adults.

The ''very rigorous study ... showed conclusively it made no difference'', he said.

''People have asked what can you do to prevent colds - well, apart from looking yourself in a room and not seeing anyone, sadly there isn't anything.''

Few people in the study had extremely low levels of vitamin D at the beginning of the research though, meaning the findings might not apply to them, and more research also needed to be done on children, Murdoch said.

The researchers were currently looking at whether vitamin D could prevent other infections, including carriage in the nose of staphylococcal bacteria.

An earlier version of this story incorrectly stated spending more time in the sun would not prevent the common cold. The researchers only studied vitamin D supplements and cannot say whether sun exposure would have an affect.